The present invention relates to a cutoff apparatus, and in particular to a cutoff apparatus adapted to cut bumper-length segments from an elongate shaped being made in a continuous roll-forming process.
Recently, an apparatus and process was invented to manufacture roll-formed tubular vehicle bumpers that are longitudinally curved or swept. (See U.S. Pat. No. 5,092,512 and U.S. Pat. No. 5,104,026). The roll-formed bumpers are made from a strip of high strength steel alloy of about 60 to 120 ksi tensile strength or more which is roll-formed into a tubular shape and swept longitudinally to form a longitudinally curved shape. The elongate shaped is then cut into bumper-length segments which are subsequently prepared as needed to form automotive bumpers or bumper reinforcement bars. The above noted process is particularly economical since high strength-to-weight bumpers can be made with very high strength materials at a competitive cost and at high production rates.
It is known to position a cutoff device in-line with a roll-forming machine to cut segments from an elongated shaped element during the roll-forming process. However, traditional cutoff devices are not adapted to sever a longitudinally curved shaped element such as a bumper made of high strength materials as in the elongated shaped bumper noted above. For example, the traditional cutoff devices utilize a track to guide the cutoff mechanism of the traditional cutoff device during the cutoff stroke. However, use of a track requires that the track be accurately aligned with the elongated shaped bumper so that there will not be any interfering misalignment between the track and the high strength elongated shaped bumper. In particular, any such interference can cause poor part quality, excessive wear on the cutoff device, and/or binding on the cutoff device. Notably, alignment is particularly difficult to achieve and/or maintain when the elongated shaped bumper is longitudinally curved. Further, use of a curved track necessarily requires that the track be changed, adjusted, and/or realigned every time the bumper-forming process is changed over to make a different bumper having a different degree of sweep. Hence, a cutoff device is desired that self-aligns with the elongated shaped bumper.
Another problem is that many traditional cutoff devices utilize a saw blade. This can result in excessive downtime caused by frequent blade changes since the bumper is made of high strength steel and has a large section to cut through. Thus, a cutoff device is desired that is long lasting, but which is maintainable by traditional die maintenance methods.
One type of cutoff device that has been used includes semi-stationary cutoff dies that are made to receive the bumper, the cutoff dies being adapted to move along the path of the bumper during a cutting stroke as a bump-press arrangement stamps the dies to shearingly cut the elongate shaped. (See FIGS. 16 and 17 labelled as prior art in the attached drawings.) The cutoff dies include cammed die slides for trimming the sides of the bumper, and also include a center die for trimming the center web of the elongated bumper. These cutoff dies require that the inside of the elongated bumper be supported so that the cutoff dies do not crush the bumper during the stamping/cutoff process. However, supporting the inside of a bumper in an exact location so that the cutoff dies can shearingly engage same is difficult if not impossible to achieve. Further, even if a way to support the inside of the tube is devised, the cutoff dies are sensitive to alignment and will tend to hang up or wear undesirably unless the dies are fully aligned with the path of the bumper. Further, the press can tend to "walk" out of alignment due to vibration from the stamping/cutoff process. This problem is compounded since the die stamping press cannot be permanently anchored to the floor, but rather must be adjustably mounted to the floor so that the location of the die stamping press can be adjusted to receive bumpers having different levels of sweep.
Another cutoff device sometimes used to cut roll-formed shapes is a traditional band saw type cutoff device. However, these devices require a track to move along a curved path, as discussed above, and further require frequent maintenance such as blade changes due to blade wear from the high strength steel used in the above noted process.
Thus, a cutoff apparatus is desired for solving the aforementioned problem. In particular, a cutoff apparatus is desired which is self-aligning, readily maintainable, long-lasting in service, and readily adjustable for different levels of sweep, but which is relatively non-complex in operation.